Centrifugal separator having a rotor and driving means thereof

ABSTRACT

In a centrifugal separator, the rotor ( 19 ) of which is adapted to be driven by means of a gaseous driving fluid, the rotor itself supports a ring of turbine blades ( 34 ) extending around the rotational axis (R) of the rotor. A stationary nozzle ( 40 ) is adapted to direct a flow of the driving fluid towards the ring of turbine members ( 34 ). After the driving fluid has passed between the turbine blades ( 34 ) and has influenced them for driving of the centrifugal rotor, it enters a reversing chamber ( 41 ) formed by a stationary reversing member ( 42 ). In the reversing chamber the driving fluid is caused to change its direction and is then conducted again towards the ring of turbine members ( 34 ) in order to be utilized a second time for driving of the centrifugal rotor.

[0001] The present invention relates to a centrifugal separator having arotor and a driving means for rotation of the rotor about a rotationalaxis by means of a gaseous driving fluid.

[0002] About 100 hundred years ago pressurised steam was sometimes usedfor driving centrifugal rotors. A steam turbine was coupled to thedriving shaft of a centrifugal rotor in one way or another, usuallythrough a gear device. Since then rotors of high speed separatorsusually have been driven by means of electrical motors.

[0003] Lately, driving of a centrifugal rotor by means of a gas turbinehas sometimes been suggested. A gas turbine operated centrifugal rotoris suggested for instance in U.S. Pat. No. 5,779,618. However, noefficient and compact arrangement for gas turbine operation of acentrifugal rotor has been seen.

[0004] The present invention has for its object to provide an efficientand compact driving means for the rotor of a centrifugal separator bymeans of a gaseous driving fluid.

[0005] This object can be obtained by means of a driving means including

[0006] turbine members connected with the rotor and arranged in a ringaround and at some distance from said rotational axis,

[0007] at least one supply member adapted to direct said driving fluidtowards the ring of turbine members in a way such that the rotor isbrought into rotation about said rotational axis by successive actuationof the turbine members by said driving fluid, and

[0008] at least one reversing member, which is adapted to receive atleast part of said driving fluid having passed through the ring ofturbine members and conduct it back towards the ring of turbine membersin a way such that the rotor once more is actuated in its rotationaldirection by such returned driving fluid.

[0009] A driving means of this kind can be made efficient, because theenergy of the driving fluid can be utilised in an advantageous way, andalso be made compact because the driving means can be integrated withthe rotor itself.

[0010] Even if it is possible to arrange the supply member for thedriving fluid so that it directs the driving fluid axially towards theturbine members, it is assumably most advantageous to arrange one of thesupply member and the reversing member radially outside the ring ofturbine members and the other one of the supply member and the reversingmember radially inside the ring of the turbine members. It is assumedthat the available space would be utilised most effectively if thesupply member is arranged radially outside and the reversing memberradially inside said ring of turbine members.

[0011] If two or more supply members and reversing members are used, itis suitable that these are distributed evenly around the ring of turbinemembers, so that a balanced loading of the rotor is obtained from theforces to which this is subjected by the driving fluid. If only twosupply members and reversing members, respectively, are used these are,thus, arranged at diametrically opposite sides of the ring of turbinemembers. This is advantageous for the life time of the bearings, throughwhich the rotor is suspended in a stationary support device, e.g. ahousing surrounding the whole rotor.

[0012] In order to make possible the most efficient utilisation of theenergy of the driving fluid it is suitable that the ring of turbinemembers is arranged at the radially largest portion of one axial endwall of the rotor. Thus, if the rotor at one axial end has a firstportion surrounding the rotational axis and situated at a first radialdistance therefrom and a second portion surrounding the rotational axisand situated at a second distance therefrom, said second distance beinggreater than said first distance, the ring of turbine members should bearranged adjacent to and at the same distance from the rotational axisas said second portion. Preferably, the ring of turbine members iscarried directly by said second portion.

[0013] The invention may be used in a centrifugal rotor intended forliquid cleaning as well as a centrifugal rotor intended for gascleaning. When it is used in connection with gas cleaning, thecentrifugal rotor is preferably surrounded by a stationary housinghaving a receiving chamber and an outlet for cleaned gas coming from thecentrifugal rotor. If so, the housing is preferably shaped in a way suchthat gas having been used for driving of the centrifugal rotor isintroduced into said receiving chamber and, thus, may leave thecentrifugal separator together with the cleaned gas.

[0014] The invention is further described in the following withreference to the accompanying drawing, in which FIG. 1 shows an axialsection through a centrifugal separator according to a preferredembodiment of the invention, and FIGS. 2 and 3 show cross sections alongthe lines II-II and III-III, respectively, in FIG. 1. The axial sectionin FIG. 1 is taken along the line I-I in FIG. 2.

[0015] The centrifugal separator shown in the drawing includes astationary housing 1 consisting of an upper part 2, an intermediate part3 and a lower part 4. The parts are kept together by means of clampingmembers 5 and 6. The upper housing part 2 forms an inlet 7 for a gas ora gas mixture to be cleaned by means of the centrifugal separator. Thelower housing part 4 forms both an outlet 8 for gas having been cleanedand an outlet 9 for material having been separated from the gas.

[0016] The intermediate part 3 of the stationary housing forms asurrounding wall, surrounding a space in the housing, and has at itsupper end an annular end wall 10 extending a distance inwardly from thesurrounding wall. The annular end wall 10 supports within the housing acentral sleeve 11, the interior of which communicates with theaforementioned gas inlet 7, that is formed by the upper housing part 2.A gasket 12 is adapted to seal between the upper housing part 2 and thesleeve 11.

[0017] The sleeve 11 supports in its said interior, by means of severalsupporting members 13 (see FIG. 2), a central hub 14. The supportingmembers 13 are distributed around the periphery of the sleeve and leavebetween themselves several passages 15 which at their upper endscommunicate with the aforementioned gas inlet 7.

[0018] On its inside the hub 14 supports a bearing sleeve 16, which inturn supports through bearing balls 17 a vertically extending shaft 18.The shaft 18 extends downwardly into the housing 1 and supports thereina rotor 19. The rotor is rotatable in the housing 1 about a verticalrotational axis R.

[0019] The rotor 19 includes a substantially conical or bowl formedupper end wall 20 and a similarly formed lower end wall 21. Both of theend walls 20 and 21 turn their concave sides upwardly towards the gasinlet 7 of the stationary housing. Between the end walls there isarranged a stack of conical separation discs 22 (only part of the stackis shown in FIG. 1), which between themselves delimit thin interspacesforming through flow passages 23 for gas to be cleaned in thecentrifugal separator. The end walls 20 and 21 and the separation discs22 are kept axially compressed on the shaft 18 by means of a screw 24and a spring 25.

[0020]FIG. 3 shows a separation disc 22 seen from above with respect toFIG. 1. The disc has a conical outer portion 26 and a central portion 27connected therewith. The central portion has a large number of throughholes 28 situated at some distance from the centre of the disc anddistributed around it. In the assembled rotor 19 (see FIG. 1) theseholes 28 form together with the interspaces between the central discportions 27 a central space 28 a communicating with the aforementionedthrough flow passages 23 between the discs 22. Furthermore, the centralportion 27 has a central non-round, in this case hexagonal, openingthrough which the aforementioned shaft 18 is to extend. As can be seenfrom both FIG. 1 and FIG. 3, the shaft 18 is surrounded by a sleeve 29extending axially between the rotor end walls 20 and 21. The sleeve 21has a circular inner cross section but a hexagonal outer cross section,so that the outside of the sleeve may be in rotational engagement withthe separation discs 22 as well as the end walls 20 and 21.

[0021] On the upper side of each disc 22 there are several rib likeprotuberances 30 which are evenly distributed around the centre of thedisc and which extend across the conical portion 26 of the disc from thecentral portion 27 to the peripheral edge of the disc. The protuberances30 serve as spacing members between adjacent separating discs 22 in therotor and also as flow guiding members during operation of thecentrifugal separator, as will be explained later. The rib likeprotuberances extend on each separating disc in a way such that theyform an angle with generatrices of the conical portion 26 of theseparation disc.

[0022] The upper end wall 20 of the rotor has a radially inner portion31, that is formed in one piece with a central sleeve 32 surrounding theshaft 18, and a radially outer portion 33. The radially inner portion 31of the end wall 20 has several through holes 31 a distributed around thecentral sleeve 32 and forming a central inlet of the rotor 19 for gas tobe cleaned. The holes or inlet 31 a communicate with the gas inlet 7 inthe stationary housing part 2 through the interior of the stationarysleeve 11. The radially inner portion 31 of the end wall 20 further hasan annular axial flange 31 b, which surrounds an end portion of thestationary sleeve 11 in a way such that the smallest possible interspaceis formed between the flange 31 b and the sleeve 11. If desired, asealing may be arranged in this interspace.

[0023] The radially outer portion 33 of the end wall 20 supports on itsupper side a ring of turbine blades 34, which extends concentricallywith the rotational axis R of the rotor (see FIG. 2). The blades 34 aresituated in a downwardly facing annular groove on the underside of theend wall 10, formed between two downwardly directed annular, concentricflanges 35 and 36. The ring of turbine blades are, thus, supported onthe radially outermost portion of the rotor.

[0024] As can be seen from FIG. 2, the two said flanges 35 and 36 do notextend circularly all the way around the rotational axis R. Thus, theouter flange 35 has two interruptions or gaps 37 and 38, whereas theinner flange 36 has one interruption or gap 39. Supported by theintermediate part 3 of the stationary housing a nozzle 40, that extendsinto the first mentioned interruption or gap 37, is adapted to receive apressurised gas and to direct a flow of this gas towards the ring ofturbine blades 34 from the outside of the ring. The nozzle 40 isdirected in a way such that the gas flow causes the blades 34 and,thereby, the whole of the rotor 19 to rotate around the rotational axisR, counter clockwise with respect to FIG. 2.

[0025] The blades 34 are somewhat arcuate, as can be seen, which is notreally necessary, and conducts the gas stream supplied between adjacentblades to the inside of the ring of blades, where the gas flow enters asmall reversing chamber 41. This reversing chamber 41 is delimitedbetween on one side a reversing member 42, that is constituted by partof the stationary end wall 10, and a plate 42 a, that is fixed to theunderside of the end wall 10, and on the other side the ring of turbineblades 34. The reversing chamber is formed in a way such that the gasentering thereinto from the interspaces between the turbine blades 34 isconducted without substantial pressure loss in a curved path a distanceforwardly in the rotational direction of the turbine blades to a certainposition and after that, again in between the turbine blades 34 situatedat this position. The pressurised gas is utilised in this way once morefor driving of the ring of turbine blades 34.

[0026] When the pressurised gas has again passed through the ring ofturbine blades 34, it flows radially outwardly through the interruptionor gap 38 in the flange 35 to an annular space 43 in the intermediatepart 3 of the stationary housing (see FIG. 1). This space 43communicates directly with a receiving chamber 44 that surrounds therotor 19 in the stationary housing 1.

[0027] As can be seen from the drawings, the part of the housing 1surrounding the rotor 19 is substantially rotational symmetric and ithas a form substantially adapted to the outer shape of the rotor. Theoutlet 8 for cleaned gas is situated in a conical portion of the housingpart 4 at the same axial height as the lower rotor end wall 21. Theoutlet 9 for material having been separated from supplied contaminatedgas is situated centrally below the rotor 19 aligned with the rotationalaxis R of the rotor.

[0028] As can further be seen from the drawing (see particularly FIG. 2)the reversing member 42 is formed in one piece with and at substantiallythe same axial level as the sleeve 14, which on its inside supports thebearing 16, 17 for the rotor shaft 18. The reversing member 42 therebyis situated radially seen between the bearing 16, 17 and the turbineblades 34. This gives the centrifugal separator a very compactconstruction with respect to the arrangement for driving and journallingof the rotor.

[0029] The above described centrifugal separator operates in thefollowing manner.

[0030] For rotation of the rotor 19 the nozzle 40 is charged withpressurised gas, e.g. compressed air, from a source that is not shown. Aflow of gas is directed by the nozzle 40 from a gas supply area, formedby the gap 37 in the flange 35 radially outside the ring of turbineblades 34, towards the outside of this ring, so that the gas flowsbetween the blades and causes these and, thereby, the rotor 19 to rotatecounter clockwise with respect to FIG. 2.

[0031] Driving gas exiting from the blade interspaces on the inside ofthe blade ring enters the reversing chamber 41, in which it is deflectedforwardly in the rotational direction of the blade ring and, thereafter,again is directed towards the blades 34 for renewed driving thereof.After having been used twice for driving of the turbine blades the gasexits through the gap 38 in the flange 35 into a space 43 (see FIG. 1),from where it flows further on out into the receiving chamber 44surrounding the rotor 19.

[0032] A contaminated gas to be cleaned from solid and/or liquidparticles suspended therein is supplied through the gas inlet 7 in thestationary upper housing part 2. The gas flows further through thepassages 15 and the rotor inlet 31 a into the central space 28 a in therotor 19. From the central space 28 a the contaminated gas flows furtherthrough the flow passages 23 between the conical portions 26 of theseparation discs 22.

[0033] Between the separation discs 22 the contaminated gas is broughtinto rotation by the rotor, particles present in the gas and having adensity larger than that of the gas being separated as a consequence ofthe centrifugal force and being brought into contact with the uppersides of the conical portions 26 of the separation discs. In contactwith these portions of the separation discs the particles move as aconsequence of the centrifugal force radially along generatrices of theportions 26, the particles or coalesced liquid particles being collectedby the inclined ribs 30. The separated particles move by means of thecentrifugal force further along the ribs 30 to the peripheral edges ofthe separation discs, from where they are thrown away from the discs andhit the surrounding wall 3 of the housing.

[0034] The gas being gradually freed from particles flows between theadjacent separation discs 22, guided by the ribs 30, towards theperipheral edges of the discs and leaves the rotor at these edges. Viathe receiving chamber 44 the cleaned gas flows out of the housing 1through the outlet 8. This outlet 8, as can be seen, is situated belowthe level at which particles having been separated from the gas arethrown away from the rotor 19 towards the surrounding wall 3. Even thegas having been used for driving of the rotor 19 leaves the stationaryhousing through the outlet 8.

[0035] As a consequence of the fact that the contaminated gas enters thecentral space 28 a in the rotor 19 substantially without rotationalmovement, whereas the cleaned gas leaves the rotor under rotation at aradius larger than the radius of the central space 28 a, anunderpressure will be formed in the central space 28 a. Hereby, thecontaminated gas need not be supplied to the rotor at an overpressure.Instead, it may be sucked into the rotor from the gas inlet 7 of thestationary housing 1.

[0036] The particles separated from the gas, solid and/or liquid, movedownwardly along the inside of the surrounding wall 3 and further alongthe conical lowermost portion of the housing 1 and out through theoutlet 9. By the shape of the outlet pipe forming the outlet 8, shown inFIG. 1, i.e. by the fact that this outlet pipe extends a short distanceinto the interior of the housing 1 and is provided with a flange, it isavoided that separated particles are entrained by cleaned gas outthrough the outlet 8.

1. A centrifugal separator including a rotor (19) and a driving meansfor rotation of the rotor about a rotational axis (R) by means of agaseous driving fluid, characterized in that the driving means includesturbine members (34) connected with the rotor (19) and arranged in aring around and at some distance from the rotational axis (R), at leastone supply member (40) adapted to direct said driving fluid towards thering of turbine members (34) in a way such that the rotor (19) isbrought into rotation about said rotational axis (R) by gradualactuation of the turbine members (34) by the driving fluid, and at leastone reversing member (41,42) that is adapted to receive at least part ofsaid driving fluid having passed through the ring of turbine members(34) and to conduct it back towards the ring of turbine members in a waysuch that the rotor (19) is once more influenced in its rotationaldirection by driving fluid thus being reversed.
 2. A centrifugalseparator according to claim 1, in which one of the supply member (40)and the reversing member (41,42) is arranged radially outside the ringof turbine members (34) and the other one of the supply member (40) andthe reversing member (41,42) is arranged radially inside the ring ofturbine members (34).
 3. A centrifugal separator according to claim 2,in which the supply member (40) is arranged radially outside the ring ofturbine members (34) and the reversing member (41,42) is arrangedradially inside the ring of turbine members (34).
 4. A centrifugalseparator according to any one of the preceding claims, in which therotor (19) at one axial end has a first portion (31) surrounding therotational axis (R) and situated at a first radial distance therefromand a second portion (33) surrounding the rotational axis (R) andsituated at a second distance therefrom, said second distance beinggreater than said first distance and the ring of turbine members (34)being arranged adjacent to and at the same distance from the rotationalaxis (R) as said second portion (33).
 5. A centrifugal separatoraccording to claim 4, in which the ring of turbine members (34) iscarried by said second portion (33) of the rotor.
 6. A centrifugalseparator according to any one of the preceding claims, in which therotor (19) has a radially outermost portion (33) and the ring of turbinemembers (34) is situated at substantially the same distance from therotational axis (R) of the rotor as this portion (33).
 7. A centrifugalseparator according to any one of the preceding claims, in which therotor (19) at one axial end has a bowl formed end wall (20) having aconcave outer side, and the ring of turbine members (34) is supported ata radially outer edge portion of this bowl formed end wall (20).
 8. Acentrifugal separator according to any one of the preceding claims, inwhich the rotor (19) includes a stack of conical separation discs (22),which have apex ends and base ends and which are arranged concentricallywith the rotational axis (R) of the rotor, the ring of turbine members(34) being arranged at an axial end of the rotor, towards which theseparation discs (22) are facing their base ends.
 9. A centrifugalseparator according to any one of the claims 3-8, in which said supplymember (40) is adapted to conduct said driving fluid towards the ring ofturbine members (34) from a supply area radially outside thereof.
 10. Acentrifugal separator according to any one of the claims 4-9, in whichthe turbine members (34) are adapted to give off driving fluid havingbeen received from the supply member (40) to a receiving area radiallyinside the ring of turbine members (34).
 11. A centrifugal separatoraccording to any one of the preceding claims, in which said reversingmember (41,42) is adapted to reverse at least part of said driving fluidtowards the ring of turbine members (34) at a reversing area situated atsome distance ahead of the receiving area, seen in the rotationaldirection of the rotor.
 12. A centrifugal separator according to any oneof the preceding claims, in which the rotor (19) is supported by a shaft(18), that through a bearing (16,17) is supported by a stationarycarrying member (14), the turbine members (34) being supported by therotor (19) and said reversing member (42) being arranged radiallybetween said bearing (16,17) and the turbine members (34).
 13. Acentrifugal separator according to claim 11, in which said carryingmember (14) is rigidly connected with the reversing member (42).
 14. Acentrifugal separator according to claim 13, in which the carryingmember (14) is formed in one piece with the reversing member (42).
 15. Acentrifugal separator according to any one of the preceding claims, inwhich the rotor (19) is adapted to be charged with a gas or a gasmixture to be freed from particles suspended therein, the rotor (19) issurrounded by a stationary housing (1), which has an outlet (8) for gasor gas mixture having been freed from particles in the rotor (19), thestationary housing (1) delimits a receiving chamber (44), that isadapted for reception of gas or gas mixture from the rotor (19) havingbeen freed from particles, and that communicates with said outlet (8),and the stationary housing (1) is shaped in a way such that saidreceiving chamber (44) is adapted for reception of driving fluid leavingthe turbine members (34) after having passed these a second time.